(CNN)It took the government shutting down to reinvigorate a little spirit of bipartisanship in the US Senate.

After three days and countless bipartisan negotiations on the floor and behind closed doors, the government has reopened. And hundreds of thousands of federal workers will be able to show up for work Tuesday.

But behind the scenes, lawmakers on both sides of the aisle -- absent clear presidential leadership -- had to scramble to try to re-open the government and put the Capitol back together.

In the end, lawmakers and senior aides credit -- or, in some cases on the Democratic side, blame -- a group of more than 20 bipartisan members for clearing the way for a breakthrough of sorts, even if re-opening the government for just a few more weeks falls far short of historic in the annals of Senate history.

Yet, re-establishing some modicum of trust that had been missing in the year since Donald Trump assumed the presidency, and by most accounts for years prior, isn't a small development, lawmakers in the group said. After brutal, partisan health care and tax fights tore the parties apart, a shutdown of all things appeared to remind lawmakers there was still room to negotiate in the middle.

Read More

"What I have seen here on the floor of the Senate in the last few days is something we have not seen for years: constructive, bipartisan conversation," said Sen. Dick Durbin, an Illinois Democrat and the minority whip.

The bipartisan group of senators met for days inside Maine Republican Sen. Susan Collins' office, spurred both by frustration and a desire to finally reopen the lines of communication.

The government shutdown lasted just under three days, but the members of the bipartisan group noted that their work wasn't just about trying pass a spending bill. In the end, it was leadership that made the tough calls about what would have to be exchanged to reopen the government.

Senate Majority Leader Mitch McConnell would say he intended to bring a real immigration debate to the Senate floor. Senate Minority Leader Schumer would reject it initially. And then a day later, McConnell would speak again and Schumer -- despite concerns from his left flank -- would vote to re-open the government with a three-week stopgap resolution, giving the rest of his conference permission to also vote "yes."

Bipartisan meetings in Collins' office

Sen. Bill Nelson, a Florida Democrat, said it was Sunday night when he saw a clear shift in the posture of the bipartisan group -- one that would culminate the next morning. "Everybody realized we were singing from the same hymnbook," Nelson told CNN of the Sunday night talks.

Inside those meetings, senators described goodwill, long hours and one disciplined meeting strategy.

Multiple senators told CNN that lawmakers had agreed to use a talking stick. The agreement was that before anyone interrupted or shared their perspective, they should be holding the stick.

For the most part, it was a success.

One senator described a lighthearted moment where the stick was passed a bit forcefully as Sen. Mark Warner, a Virginia Democrat, began to ask a question and interrupt his Republican colleague, Sen. Lamar Alexander of Tennessee. When the stick was passed -- or "tossed with some enthusiasm," one senator recalled with a chuckle, it caused a tiny bit of damage to a shelf where an elephant figurine was sitting in Collins' office.

The source told CNN all the senators laughed about the incident, and after that, Collins replaced the stick with a small rubber ball. Alexander countered later by bringing a mini basketball from his office as a joke, and the senators started using it.

"There were no injuries, there were a couple close calls but everything worked out fine," one Republican senator said about the talking stick.

Another Republican senator joked, "That was the most entertaining meeting I'd ever been to."

Members in the bipartisan group said the lengthy and substantive discussions they had for several days tucked in a corner office in the Dirksen Senate Office building were about finding trust and establishing that there would be a solid foundation to negotiate immigration, appropriations and more once the government reopened.

"The trust deficit on those issues is a key problem," said Sen. Chris Coons, a Democrat from Delaware. "What we were able to come out of this with is a clearer path forward toward actually working together and resolve a whole suite of larger issues. Yes, we both built confidence and built trust, but went back and forth with specific and concrete proposals. How long should the CR be? What kind of language might the leadership use on the floor? What kind of process could we use?"

Connecting leadership

The group also acted as emissaries for leadership. While McConnell and Schumer didn't speak all day Saturday after the shutdown and only briefly on Sunday evening, members in the bipartisan group were keeping their leadership apprised of the discussions they were having. At one point, while shuffling in between offices on Sunday, Sen. Lindsey Graham of South Carolina -- dressed in a very weekend outfit of khaki pants, a fleece jacket, running shoes and an orange Clemson hat -- was seen grabbing a handful of Hershey's Kisses from a bowl on his way into McConnell's office. Given the sheer number of visits Graham made to the office in pursuit of a resolution, one aide wondered if McConnell's candy stash could withstand a lengthy shutdown.

Nelson described that throughout the process, Schumer was always willing to listen to their ideas and proposals, even if it wasn't always clear they could form the basis of an eventual deal.

"Schumer was always receptive," Nelson said. "Because Schumer wanted something that would work and he knew that the present course we were on, at the end of the day, we didn't have the majority and we didn't have the White House, so we didn't have a lot of cards to play."

Many of the bipartisan members who met this shutdown had also worked together to end the more than two-week shutdown in 2013. Their discussions with leadership and their open lines of communication seemed to have an effect.

On Sunday night, for example, after Majority Leader Mitch McConnell went to the Senate floor to say he intended to bring up immigration for debate, multiple Democratic aides made it clear that that offer was insufficient because it used phrases like "intention" instead of more definitive words that would make it clear McConnell's commitment was ironclad.

Then, on Monday morning, Collins said publicly she thought it would be a good idea for McConnell to be clearer about his commitment to the Democrats.

A McConnell aide said they took Collins' comments to heart. And while they did not make any substantive changes to his statement on the floor this morning, they did try to have McConnell phrase it in a more plainspoken, direct and real manner, to be more convincing to the Democrats.

In the end, it was Collins and Flake -- both members who had been promised things from McConnell during the tax debate and were still awaiting their commitments to be carried out -- who helped convince their Democratic colleagues that they could trust McConnell's word.

Democrats' left flank left dissatisfied

Still, the shutdown revealed some schisms within the Democratic Party.

In the end, there were more than a dozen Democratic senators who voted against the three-week continuing resolution. Those members included many of the progressives in the party and potential 2020 candidates like Sens. Elizabeth Warren of Massachusetts, Kamala Harris of California and Kirsten Gillibrand of New York.

In a caucus meeting just before the vote on the three-week continuing resolution Monday, Schumer made the case to his members that he'd gotten McConnell to move on immigration and still had other points of leverage: Still to come were the budget caps agreement where Republicans want a lot of money for defense; the next continuing resolution; and the March 5 DACA deadline that he said the GOP is fearful of breaching because they don't want to take the hit for seeing DACA recipients deported, according to a source in the room.

Sen. Jeff Merkley of Oregon was one of the liberal senators who voiced objections to this strategy of accepting the McConnell deal, raising concerns that the party gave in way too much without extracting much from Republicans and would lose the support from liberal groups, two sources said.

Merkley later met with liberal activists who were furious at Schumer and warned that they would withhold funding from Democrats in key races, one source said.

At the Democratic caucus meeting, Sen. Dianne Feinstein was upset that she had to cast a vote to shut down the government Friday. Why couldn't this be resolved then, she asked?

In the end, a bipartisan vote, 81-18, reopened the government. Democrats involved in the bipartisan talks, aides said, knew the fury they would kick up among both the party activists and even members of their own caucus. But the down payment on a potential long-term shift in the posture that defines the Capitol these days -- zero-sum games, partisan brawls and victories defined only by which side was later drubbed the most -- brought more optimism to the Senate floor than many had seen in years.

Bipartisan groups have been created, touted and fallen flat before. Given the hyper-intense nature of US politics -- and an election year already kicking into full gear, skepticism about the future is merited.

Yet Nelson, asked if the group could form the baseline for future deals and positive, or at least collegial, sentiment in a chamber that has been rife with partisan warfare and divisiveness for years, clasped his hands together as if in prayer and looked upward. "Oh please. Please. Please. That this could be the beginning of a new day."

Senators Joe Manchin (D-WV) and Susan Collins (R-ME) lead a group of bipartisan Senators as they speak to reporters after the Senate passed a procedural vote for a continuing resolution to fund the federal government on Monday. (Photo by Drew Angerer/Getty Images)

After the vote, Collins, West Virginia Democrat Joe Manchin, Graham, Minnesota Sen. Amy Klobucher, Alaska Sen. Lisa Murkowski, North Dakota Democratic Sen. Heidi Heitkamp and others all gathered outside the Senate chamber where they congratulated each other in front of cameras for being able to pass a vote to end the shutdown.

Graham joked with reporters that Collins' office had been "Switzerland" throughout the whole process.

"By opening up the government, we stopped losing," Graham said. "We have not won until we have a result. Susan's office is Switzerland. This is the one place we can all go and feel good. This is my first visit with the group. I enjoyed it but you share your feelings way too much for me."

Later, after the shutdown freshman Democratic Sen. Doug Jones, who voted for the continuing resolution, recounted his first major event in the US Senate.

"I feel like I've been hazed as a freshman," he told reporters, smiling.